Messages in this thread | | | Date | Wed, 06 Aug 2008 15:17:38 +0400 | From | Sergei Shtylyov <> | Subject | Re: Kernel Summit request for Discussion of future of ATA (libata) and IDE |
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Hello, I wrote:
>>>>>> supported. I couldn't track down where that bit was actually >>>>>> defined in the first place, all the way back to ATA-1 it seems to >>>>>> be indicated as reserved. Actually, I'm not sure why the drive >>>>>> cares in the first place, it would seem like a pure host >>>>>> controller issue.. >>>>>> >>>>> It goes back before IDE into the depths of the original compaq >>>>> spec. When >>>>> you have a device wired basically directly to the ISA bus >>>>> (original IDE) >>>>> >>>> ISA has only 8/16-bit data bus, so it could not have mattered >>>> there... >>> >>> Depends what a 32bit I/O looks like on the 16bit bus - timing wise. >>> >> >> Two 16-bit reads at addresses 0x1x0 and 0x1x2 with the programmed >> recovery time, IIRC... It's just occured to me that in case of the >> 16-bit bus it should be how the drive treated the accesses at address >> 0x1x2 with IOCS16 asserted that could have mattered. If it honored >> them, 32-bit I/O could have worked even on a dumb ISA "controller", >> if not -- no way (unless you really had *something* between the ISA >> and the IDE cable). > > Oh, -IOCS16 is driven by device, not host. I give up then. :-) >
OTOH, it definitely could work if the drive asserted it for the I/O port 0x1x2 at least for the data transfer phase (and probably even if it always asserted -IOCS16 for this address). That pre-historic word indeed could have made sense then...
MBR, Sergei
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